Grain grinder



Nov. 3939. H. M. JOHNSTON 2,178,636

GRAIN GRINDER Filed Oct. 25, 1937 uwewrom HOWARD M- JOHNSTON A TTOR/VEXPatented Nov. 7, 1939 UNlT ED s'm'rs s ATENT OFFICE GRAIN GRINDERApplication October 25,

2 Claims.

This invention relates to grinding or crushing machines for grains andthe like andmore particularly to machines of the type which employplates for grinding purposes.

In the grinding of hard grains, overfeeding frequently occurs and thegrinding plates become heated up resulting in the caking of grain in thegrooves. The grinding operation of the machine and its capacity aretherefore adversely affected, and frequent inspection and adjustment arerequired. It has been proposed to associate a clutch with the feed wormarranged to release when pressure on the plates reaches a certain point.Such an arrangement, however, is complicated in construction and alsocalls for frequent adjustment to maintain. the desired capacity.

It is the object of. the present invention to provide a grinder having aresilient means associated with the feed worm whereby the feed Worm isyieldable in a longitudinal direction in response to certain pressures.Another object is to provide means for adjusting the tension of theresilient means whereby the yielding pressure of the worm may be variedfor different types of grains.

The invention will be described with reference to the accompanyingdrawing, in which,

Figure 1 is a sectional elevation of the grinder, and

Figure 2 is a cross-section of the feed worm.

In the drawing, I is a feed hopper supported in a frame 2 of thegrinder, 3 a feed worm positioned in the frame at the hopper outlet andcarried by a driven shaft 4 suitably mounted in bearings 5 in the frameto be driven by means of pulley 6, and l and 8 the grinding plates alsomounted in the frame I.

The grinding plates and their mounting in the frame are of usualconstruction and form no part of the present invention. Plate 1 isbolted to the frame as shown and plate 8 is bolted to a disc 9 keyed tothe shaft 4 by means of key I which is mounted within hub 9'. The keyI!) cooperates with a short groove II in the shaft whereby a slightaxial movement of the disc is permitted. The disc is provided with a hub9' against which a drum member l2 presses. The drum I2 is resilientlymounted on the frame 2 by means of bolts l3 and springs M in a mannercommonly employed in the art. A cap is secured to the drum l2 andan'adjusting screw I6 is threaded axially through the cap. Mounted onthe inner end of the screw is a bearing member I! having bearingengagement with a 1937, Serial No. 170,820

ball race 23 cooperating with a corresponding ball race 29 mounted onthe reduced end-30 of the shaft 4. A pin 35 passing through the shaftmaintains the ball races in position thereon. A locking nut i8 isprovided for the screw 16. 6 When it is desired to adjust the machinefor coarse grinding, the locking nut I8 is moved to permit turning ofthe screw 16, which is rotated in a counter-clockwise direction. Suchrotation of the screw causes leftward movement thereof carrying with itthe member I I out of engagement with ball race 28. As grinding begins,the clearance between member H and ball race 28 is taken up by axialmovement to the left of shaft 4 with disc 9 under pressure of grain anda corresponding clearance effected thereby between plates 7 and 8. Forfine grinding, the screw i6 is rotated in the reverse direction toreduce the clearance between the plates. It will be observed that disc 9with plate 8, under a predetermined high pressure such as might becaused by entrance of a stone or like hard obstruction into the spacebetween the plates, may move to the left against the action of springs Mas permitted by its key connection It! with groove H in the shaft. DrumI2, cap l5, screw l6 and member I'l also all move leftwardly with plate8, returning to their predetermined position under the action of springsI4 when the obstruction is dislodged.

The feed worm 3 is positioned in a substantially cylindrical housing [9formed integral with the frame and is keyed to the shaft 4 for slidableaxial movement therealong. As shown in Figure 2, keys 20 in the wormcooperate with grooves 2| in the shaft. One end of the worm bearsagainst the hub 9' of the disc 9 and the other end is formed with aflange 22 of the same diameter as the worm. A spring 23 of substantiallythe same diameter as the worm is positioned in the rear end of thehousing l9 and hears at one end on the flange 22 and at the other end ona disc 24 which is adjustably mounted on the shaft as by screws 25. Theaxial leftward thrust of spring 23 is much less than the combinedrightward thrust of all of the springs [4.

The outlet of hopper I is provided with an inclined plate 26 to directthe grain onto the feed worm.

Grease cups 2! are provided for the various bearings.

In operation, with the plates suitably adjusted for the grain to beground, the tension of the spring 23 is adjusted to the yieldingpressure desired for the worm having regard to the na ture orthe grainto be ground; Whenjor any, reason excessive pressure occurs on theplates the worm slides rearwardly along the shaft to relieve thepressure, caused by obstructions and the like or by overfeeding. Itshould be stated that, due to the yieldable mounting of the worm, nooverfeeding can result Thus the worm is made much larger in diameterthan in the usual typeiof machines of the same power and size ofgrinding plates, and the machine therefore grinds a much greater amountof grain in the same space of time, The large diameter worm feeds thegrain at a capacity rate to the plates at all times, any excesv ,sivepressure being absorbed by thespring 23.

It will be observed that, when excess pressure occurs in the'g'rindingzone, the worm, while continuing to rotate with the shaft andwithout interruption of the grinding action, moves to the right (asshown in the drawing) relieving the pressure within the grinding zone,and thus damage is avoided.

It will be noted that the coils of spring 23 are of the same diameterand are inclined'in the same direction as the worm 3 and, since thespring revolves with the orm, the spring serves to carry out anyparticles of grain which may work past the flange 22 into the rearwardportion of housing l9. Thus the spring maintains the latter portion ofthe housing free from accumulations of grain.-

I claim:

1. A grinder comprising a grinding chamber having a feed opening, apairof grinding plates in thechamber, a feed-worm housing in alignmentwith said feed opening, a driving shaft "carrying one of said grindingplates and extemhng Such a pressure may be 7 ing adjacent said feedopening, a feedwo'rm keyedto the shaft for longitudinal movementtherealong and normallypositioned in the latter end of the housing inalignment with said feed opening, a spring in the end of the housingremote from said hopper discharge and bearing upon the worm to urge thelatter into said feed opening, said end ofsthe housing remote from; thehopper discharge being of sufiicient length to accommodate retraction ofthe feed worm .thereinto out, of alignment 'with the hopper discharge. pt t t 2. A grinder comprising a grinding chamber having a feedopening',a pair of grinding plates in the chamber, a cylindricalfeed worm Housingin axial alignment with said feed opening, a continuously driven shaftcarrying one of said grinding plates and extending through said housingand grinding chamber, a hopper above said housing having a dischargeopening into the end ofthehousing adjacent said feed opening,

a feed worm normally positioned in the latter end of the housing inalignment withtand ex:-

tending into said feed opening, said feed worm being keyed to the shaftfor continuous rotation with it and movable longitudinally thereof, aspringin the end of the housing remote from said hopper discharge andbearing upon the worm to urge the latter'into said feed opening, saidend 01. the housing remote from the hopper discharge being of suflicientlength to accommodate retraction of the feed worm thereinto out fof thefeed opening and out of alignment with the hopperdischarger I g HOWARDMILTON J GHNSTON. I

through said housing and grlmhng chamber, a hopper above said housinghaving I v a discharge openinginto theend ofgthe hous+ I

